The present invention relates to a process for preparing white oils by hydrogenating polymers derived from olefin units having 4 carbon atoms.
White oils usually are mineral oils which are prepared by high purification of petroleum fractions boiling in the lubricating oil boiling range. This process usually comprises two steps: a desulfurization followed by hydrogenation under very severe operating conditions. White oils are allowed to be used in or in contact with food only if they fulfill the official requirements for foodstuffs. The most widely applied standards correspond to the official requirements in the U.S. regulations promulgated by the FDA, the German regulations set forth in DAB VII and the British regulations set forth in the B.P. acid test.
It has already been proposed to purify polymers which are prepared from olefin units having 4 carbon atoms, particularly polybutenes, by means of a hydrogenation process, in order to obtain a colorless and substantially odorless polybutene which can be used, for example, as a substitute for natural squalane in cosmetic formulas. However, the product obtained does not come close to fulfilling the white oil requirements. Indeed, the iodine value of the hydrogenated product, which characterizes the unsaturation degree of the product, is much too high.
German Patent Application No. 2,360,306, teaches the hydrogenation of polybutene at a temperature of between 150.degree. and 230.degree. C and at a pressure of between 15 and 35 atmospheres, in the presence of nickel or palladium on kieselguhr, but the iodine value of the hydrogenated product is about 1.
U.S. Pat. No. 3,100,808, teaches the hydrogenation of polybutene under operating conditions similar to those described in the hereabove German patent application, in the presence of nickel, palladium or platinum on alumina, but the iodine value of the hydrogenated product is higher than 1. Such iodine values are absolutely too high in order for the hydrogenated product to fulfill the white oil requirements.